In the FAQ's section, it is stated that a puppy should be able to hold their bladder for a certain length of time depending on her age. We have Rex, an almost 6-mo-old puppy who isn't able to hold his for more than a 1/2 hour when he's awake and playing.
The time frame listed isn't for when they are awake and playing....it's for when they are crated/sleeping. Because they aren't moving around while they are crated, they are more relaxed and it's easier to hold it. So the time frames listed don't really apply to play time. Basically it's saying that Rex SHOULD be able to be in his crate for up to 7 hours. There's NO WAY he could do that while awake and playing.
He doesn't seem to be grasping the concept of asking to go outside, in spite of our frequent trips, bell training, etc.
How long have you had him, exactly? Are you completely freaking out giving him lots of crazy praise when he goes outdoors (even treats, if necessary)? He has to know that going outside is AWESOME!! That's the first step.....after he learns that it is awesome to pee outside, he can learn that it is NECESSARY to pee outside! One step at a time.
Is there a way to "train" his bladder to hold it longer??
Should I be holding back water to help keep his bladder from getting so full?
There isn't really a way to train his bladder to hold it longer....you've just go to make completely sure that he understands that he is supposed to go outside. Given that he was mistreated before, chances are good that he doesn't have a good foundation for potty training, so it's probably not fair to compare him to another 6 month old who's been given good solid training since 8 weeks (or 10 weeks, or whatever).
I would not with hold water from him unless he is having accidents in his crate during the night. I did have to with hold water from my boy when he was first home because he was having issues not peeing in his crate....but I wouldn't have done it otherwise.